1. Field of the Invention
The present invention relates to a light emitting array unit having light emitting elements, and a side printing device. More particularly, the present invention relates to a light emitting array unit having light emitting elements, and a side printing device, which have a simple structure and in which quality in emitting light can be high.
2. Description Related to the Prior Art
A process of manufacturing photosensitive material, such as photo film, includes a step of side printing for printing information to a side portion of the photosensitive material in a form of a latent image. The information has forms of at least one of letters, numbers, indicia, bar code or the like, and represents a name of the manufacturer, the ISO sensitivity and the like. The latent image is converted to a visible image by developing operation for developing the photosensitive material. At the time of producing photographic prints, the information can be read or checked directly by the naked eye of an operator, or an automatic reader device.
JP-A 2-100043 discloses an example of side printing head assembly for side printing to a side portion of the photosensitive material. The side printing head assembly includes a light source, which includes plural LEDs (light emitting diodes) for emitting light of different wavelengths. Optical fibers having a great diameter include an entrance surface, which is opposed to the light source. A plurality of optical fiber bundles having a small diameter is connected to an exit surface of the optical fibers by fiber coupling. Light from the light source is caused to exit through the exit surfaces of the optical fiber bundles.
The optical fibers mix up uniformly the colors of light emitted by the LEDs as light source. The optical fiber bundles form shapes of pixels. Exit surfaces of the optical fiber bundles are oriented perpendicularly to feeding of the photosensitive material. In synchronism with feeding of the photosensitive material, the LEDs are driven to emit light selectively. The latent image of the letters, numbers, indicia, bar code or the like is printed to a side portion of the photosensitive material through a lens constituting an optical system for the side reduction.
Also, U.S. Pat. No. 4,508,438 (corresponding to JP-A 58-219543) discloses another structure of the side printing head assembly. An LED array includes plural LEDs, is opposed to the photosensitive material, and extends perpendicularly to feeding of the photosensitive material. Each of the LEDs in the LED array corresponds to one of the pixels constituting the latent image, and is connected with an LED driver, and is driven selectively to illuminate according to a pixel position designated in the sequential driving. A pattern is created by sequential driving, and is focused on to the side portion of the photosensitive material by a lens that is an optical system for size reduction. In synchronism with feeding of the photosensitive material, the LEDs are selectively driven one after another, to print the latent image of the letters, numbers, indicia, bar code or the like to the side portion of the photosensitive material.
However, the known structure according to the above first document has a shortcoming. The side printing head assembly including the optical fibers has such problems as diminution of the light amount in the optical fiber bundles, a considerably large space of the entire apparatus due to the structural complexity, a high manufacturing cost, and the like.
On the other hand, the known structure according to the above second document has a shortcoming. Light beams emitted by adjacent two of the LEDs are mixed at least partially, to cause problems of irregularity in the light amounts between the pixels, irregularity in patterned dots, and other unwanted states of light. Also, the LEDs must be disposed in a very high number per unit area, and causes difficulties in producing a wiring pattern on a printed circuit board. It may be possible to prevent such problems by spreading an interval at which the LEDs are arranged. However, a pitch of pixels in the latent image will be greater, so that the quality in printing will become remarkably low.